Abstract:
The Gudui area in southern Tibet is located in the northeast section of the Himalaya belt, the south of the Yarlung Zangbo River suture zone, and the southeast of the cuomei large igneous province.The basic rocks in the area are widely distributed, mainly located in the Jurassic-Triassic strata.In order to explore the origin and structural dynamic background of basic rocks in Gudui area, zircon U-Pb chronology and rock geochemistry of basic rocks in the area are studied in this paper.The results show that the SHRIMP zircon
206Pb/
238U isotopic dating shows that the weighted average age of diabase is 137.7±0.9 Ma, and the weighted average age of gabbro is 133.8±0.8 Ma, its formation age is early Cretaceous, which is similar to that of OIB basic rocks in Cuomei igneous Province(130~136 Ma).Rock geochemical evidence shows that the basic rocks have high TiO
2 and P
2O
5 characteristics, not Nb-Ta groove characteristics, and the trace element ratios(Ce/Zr, Zr/Nb, Zr/Y, Th/Yb)and rare earth distribution patterns are similar to those of intraplate ocean island basalt(OIB).The comprehensive study shows that the basic rocks in gudui area originated from the enriched mantle, and the basic magma was not contaminated by the crust during the upwelling process.It was formed in the intraplate tectonic environment and may be the product of the early activities of the Kerguelen mantle plume.Through this study of basic rocks in Gudui area, geological chronology and rock geochemistry evidence are provided for further understanding the genesis and tectonic background of Early Cretaceous basic rocks in the southern Tibet.